Coast & Sustainability

On the Marsh: The Largest Ecological Restoration Project in Trustees History

In early 2020, The Trustees began restoration work on portions of the 20,000-acre Great Marsh—the largest contiguous stretch of salt marsh in New England—using an innovative nature-based technique.

Barely two years later, the effort on the North Shore has become the largest coastal or ecological restoration project in the organization’s 130-year history.

Originally launching at an 85-acre pilot area at Old Town Hill in Newbury, the project aims to restore the natural hydrology of the marsh by repairing agricultural ditches dug during colonial times for salt marsh hay production. During the Great Depression, vast re-ditching programs were launched to drain the marsh in areas viewed at the time as swampy, nuisance land. By the late 1930s, nearly 94 percent of New England salt marshes had been re-ditched, negatively altering the health of this important habitat.

More than 80 years later, these ditches continue to disrupt natural tidal flow and draining processes. “A healthy marsh is a marsh that allows water to come in during high tide, and drain itself of that water during low tide, without retaining standing water,” said Russell Hopping, Trustees Lead Ecologist, Coastal Ecology. “The marsh needs to flood, but if it retains too much water it will drown the plants, killing them, which over time causes the marsh to subside due to root loss.” But by using an innovative technique pioneered by the U.S. Fish and Wildlife Service and Geoff Wilson of Northeast Wetlands Restoration, the project’s lead contractor, a natural process can heal these damaged ecosystems.

The process—which is expected to take three-to-five years—begins with “runneling” in the winter: creating shallow channels that drain any accumulated surface water as a result of clogged ditches. In spring, the process continues by layering the base of a pre-determined number of ditches with marsh grasses, cut from above. Once loosely secured into the ditches using stakes and twine, sediment borne by tides can accumulate and build marsh peat naturally. This raises the base of the ditches high enough to allow new grasses to take root and thrive, healing the delicate balance of flooding and draining. The water that used to flow through the restored ditches is diverted to the remaining ditches, keeping them clear of clogs and forcing sediment to the marsh surface, allowing the marsh elevation to increase and enabling healthy plant growth. Restoring the natural flooding process means nature does the heavy lifting, and the marsh keeps pace with sea level rise without ongoing, expensive, and disruptive interventions.

Old Town Hill marsh from above

Old Town Hill

The pilot program received a boost from a National Coastal Resilience Fund grant in 2019, expanding the project scope to 358 acres. In spring 2021, a $1 million grant from the North American Wetlands Conservation Act (NAWCA) quadrupled the Great Marsh acreage The Trustees can restore using this technique, expanding the scope of the project to a total of 1,274 acres of marsh in Newbury, Essex, and Ipswich. The additional marsh funded through the NAWCA grant is owned by three entities: The Trustees (689 acres), Essex County Greenbelt (141 acres), and the Massachusetts Division of Fisheries and Wildlife (86 acres).

Regular mosquito monitoring at the Old Town Hill site has already indicated improvements, with a year-over-year percentage of “dry” areas (where no standing water occurs to sample larvae) increasing from 8.9 percent in 2020 to 25 percent in 2021—a statistically significant decrease in standing water on the marsh, as its natural draining processes begin to heal. And in December 2021, final permits were received for restoration work to begin on the expanded acreage in Ipswich, Essex, and Newbury, just as the second year of restoration draws to a close at Old Town Hill. The Trustees now has 358 acres fully permitted—with 916 more acres in the planning phase— following the completion of design and initial monitoring work.

“The restoration process is going well, and we’re working out a few issues that were not encountered in the pilot projects,” noted Wilson. “An encouraging sign that we’re seeing is a slow reintroduction of tidal exchange into the large mega-pools, which has resulted in 7mm of sediment being deposited on the marsh surface—mimicking the way nature would ‘build up’ a healthy marsh surface over time.”

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